Andrew GliksonEarth and paleo-climate scientist
Australian National University
The ice began to form about 34 million years ago, by the late Eocene, when the Antarctic continent (Fig. 1) became isolated through the opening of the Drake Passage between the Antarctic peninsula and southern tip of South America, restricting access of warm currents, and when global carbon dioxide levels decreased to below 450 parts per million CO2, decreasing the mean temperature of Earth by near -6 °C .
Fig. 1. The Antarctic continent from space
The current global rise in atmospheric CO2 levels to 387 ppm (over 400 ppm-e radiative equivalent of CO2 + CH4 + N2O) ensues in warming of the Antarctic ice, in particular of western Antarctica, and of the Antarctic peninsula (Fig. 2). It further reduces concentration of circum-Antarctic sea ice (Fig. 3). Another expression of warming is the accelerating movement of glaciers, where the mass of the ice sheet decreased significantly at a rate of 152 ± 80 cubic kilometers of ice per year .
Based on a combination of ground stations and satellite observations, NASA/GISS reports a mean temperature increase of +0.12 °C per decade for the entire continent of Antarctica, and +0.17 °C per decade for western Antarctica, during 1957-2006 (NASA, 21.1.2009) (Fig. 2). Manifestations of warming include reduced concentration of sea ice around parts of
Fig. 2. NASA Goddard Institute of Space Science, 21.1.2009. Satellite and ground station data confirm 50 years of west Antarctica warming. Values in °C over 50 years.
Fig. 3. Sea ice per cent concentration trends in the Arctic Sea and around Antarctica for October 2008 relative to 1979-2000 October monthly average. National Snow and Ice Data Center.
Regional changes in atmospheric circulation and associated changes in sea surface temperature and sea ice are required to explain the enhanced warming in
Fig. 4. Satellite images shows the Wilkins Ice Shelf as it began to break up. The large image is from March 6; the images at right, from top to bottom, are from February 28, February 29, and March 8. NSIDC processed these images from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, which flies on NASA’s Earth Observing System Aqua and Terra satellites.
The southward migration of climate zones by nearly 400 km and the retreat of the Antarctic wind vortex (Fig. 5) have combined to increase drought conditions in southern
Figure 5. The Antarctic wind vortex viewed from the Galileo spacecraft. As climate zones migrate toward the poles, the southward contraction of the swirling cold moist fronts results in reduced rainfall over southern
Loss of Antarctic ice shelves and ice sheets, indicated by time variable gravity show mass loss  threatens to raise sea levels on the scale of many metres, leading to inundation of coastal regions, deltas, and low river valleys around the world (Fig. 7). Melting of western Antarctic ice would raise sea levels by nearly 7 metres, whereas melting of the entire Antarctic ice sheet would raise sea levels by some 70 metres, returning the Earth to pre-late Eocene conditions (Fig. 6).
Figure 6C. Maximum temperatures for
Fig. 7. Projected sea level rise (Hansen, 2007). The color bars represent topographic elevations in metres. Sea level rise by up to 25 metres (
Until recently, whenever climate research organizations reported increases in Arctic Sea ice melt rates , advocates of global “cooling” have been making references to the Antarctic continent as a supposed counter argument . Referring to small, stable or slightly cooling parts of east Anarctica (Fig 2), a plethora of bogus climate websites claims Antarctic warming is not a part of global warming .
Nor do “climate skeptics” shed too many tears about Emperor penguins, the magnificent birds which have to migrate from their inland colonies across ice shelves and sea ice (Fig. 8), where the females lay just one egg that is tended by the male. The ice plays a major role in their overall breeding success. Further, the extent of sea ice cover influences the abundance of krill and the fish species that eat them – both food sources for the penguins.
Misreadings of climate science by “climate skeptics” have delayed efforts at climate mitigation by at least 20 years. In the words of Clive Hamilton : “If scientific advances cause scientists to reject the conclusions of past IPCC reports … not much harm will be done. … but if … fellow skeptics were successful in stopping policies to cut emissions and the IPCC projections turn out to be correct, then environmental catastrophe will follow and millions of people will die. Do they lose sleep over this? Do they worry about how their grandchildren will see them? Or are they so consumed by the crusade that they know they will never be proven wrong?”
Fig. 8. Melting Antarctic iceberg.